1. Field of the Invention
The subject invention relates to a light emitting assembly of the type including light emitting diodes (L.E.D.s), and more particularly, to the avoidance of temperatures causing early degradation of the L.E.D.s.
2. Description of the Prior Art
The light emitting assemblies of the type to which this invention pertains include a plurality of L.E.D.s disposed on a mounting surface and surrounded by holes in the mounting surface. An example of such an assembly is disclosed in the U.S. Pat. No. 6,753,553 to Jiahn-Chang. The Jiahn-Chang patent discloses a light emitting assembly including a plurality of uncovered L.E.D.s disposed on the mounting surface of a circuit board defining uncovered holes located within the perimeter of the circuit board. The L.E.D.s may become damaged by water or environmental contaminants, especially in outdoor applications. The holes may become clogged with debris or other harmful objects, which impedes the flow of air through the holes.
The light emitting assemblies of the type to which this invention pertains also include a cover to protect a plurality of L.E.D.s mounted on a heat sink. An example of such an assembly is disclosed in the U.S. Pat. No. 5,857,767 to the present inventor, Peter A. Hochstein, which is directed to effective thermal management. The Hochstein '767 patent discloses a single transparent cover being large enough to cover and protect a plurality of L.E.D.s disposed on a heat sink. The single cover protects all of the L.E.D.s disposed on the heat sink from contaminants. In some configurations and uses, a single cover limits convective cooling because heat emitted from the L.E.D.s is not effectively transferred away from the L.E.D.s to surrounding air.
The prior art assemblies do not always sufficiently thermally manage light emitting diode assemblies while protecting them from the environment. As the power densities of covered L.E.D. assemblies continues to rise, the need for more effective thermal management increases. The cost-benefit calculus of light emitting assemblies is marginal unless the L.E.D.s are protected from the environment and the useful life of the L.E.D.s is at least seven years. Unfortunately, many assemblies disclosed in the prior art and currently in production operate at junction temperatures approaching 100 degrees Celsius, which virtually assures early degradation of the L.E.D.s.